It is a well established practice to provide interlocking elements that may be pile-driven into the ground, for example along a river bank, to prevent the bank from crumbling, and collapsing into the river.
The elements of these conventional barriers comprise lengths of steel sheet material, the cross-sectional shape of which is produced by rolling the sheet between rollers. The cross-sectional shape of the element generally includes changes of plane, so that the element is resistant against buckling. The cross-sectional shape is generally also provided, along the edges of the element, with hook-like formations, whereby the element may interlock with adjacent elements.
Such barriers have not hitherto been waterproof, in that the hook-like formations have permitted a leakage flow of water to take place through the assembled barrier. Previous proposals for designing waterproof barriers are shown in EP-0129275 (CORTLEVER, Dec. 27, 1984; GB-1301320 (NEDERHORST, Dec. 29, 1972); and GB-0518727 (DALRYMPLE-HAY, Mar. 6, 1940). Other relevant publications from the art of pile-driven barriers include WO-86/05532 (PROPILAFROID, Sep. 25, 1986); GB-1427060 (SOLVAY, Mar. 3, 1976); GB-0640335 (WILLIAMSON, Jul. 19, 1950); and GB-0208022 (KOHLER, Dec. 13, 1923).
The above designs have not proved efficacious, primarily on the ground of reliability of the seal, and also cost. If a spill of a groundwater contaminant is made, and if it is determined that the spill must be contained behind a waterproof barrier, the expense can be enormous. Often, a barrier will comprise four plane walls, joined at the corners to make a rectangle, and thus the barrier will surround the zone of pollution, and fence it in. Sometimes, the barrier may not need to form a complete enclosure around the contaminant--where, for example, the requirement may simply be to divert a flow of polluted groundwater away from a well.
The invention is aimed at providing a barrier which can be rendered reliably waterproof in a less expensive manner than has been possible hitherto, from the standpoints both of materials cost and of installation cost, yet which is reliable and effective.
Apart from low cost, other aims of the invention are as follows: to reduce the disturbance of land during installation; to reduce shifting of the soil, which might be damaging to surrounding buildings; to reduce installation time; and to reduce the amount of heavy construction equipment needed.
It is recognized that it is not practicable to apply a sealing material to the element, prior to the element being driven into the ground. Even if the act of pile-driving the element does not actually damage the sealing material, the risk of such damage is high, and the engineer would not dare to take the chance since the cost of repairing a leaky barrier can be enormous. On the other hand, it has been perceived as very difficult to apply a sealant to the joints between elements once the elements have been driven into the ground.